Master's lecture in Bioengineering - Libardo Lugo

Master's student: Libardo Lugo

Title: Microalgae Biomass Production Coupled with Phycoremediation of Aquaculture Wastewater

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Faculty: Faculty of Industrial Engineering, Mechanical Engineering and Computer Science

Advisor:  Ragnheiður Inga Þórarinsdóttir, Adjunct Professor at the Faculty of Civil and Environmental Engineering

Also in the masters committee: Sigurður Brynjólfsson, Professor at the Faculty of Industrial Engineering, Mechanical Engineering and Computer Science

Examiner: Halldór Svavarsson, Professor at Reykjavík University

Abstract

Large volumes of aquaculture wastewater are discharged every day directly into the environment, causing pollution of freshwater and saltwater ecosystems. This wastewater is rich in nitrogen, phosphorus, organic carbon, and other elements. These chemicals, on the other hand, are essential for microalgae. Thus, due to the potential of aquaculture wastewater to be used as a microalgal growth medium, in this project, experiments are performed to evaluate the behavior of Chlorella sorokiniana when it grows in this wastewater. The experiments performed test the microalgal growth on untreated vs. pretreated wastewater; on pH-controlled vs. pH-uncontrolled conditions; and its growth when different airflow strengths are applied to the cell suspension in the photobioreactor columns. As a result, it was found that C. sorokiniana cultures can reach a high cell density when it grows in aquaculture wastewater (82 million cells per milliliter or a biomass DW of 2.60g/L);  however, lower the obtained when the microalgae grows in synthetic medium (3.41g/L). For successful cultivation of the microalgae, the  wastewater needs to be sterilized before inoculation, and the pH needs to be controlled. Furthermore, the maximum microalgae growth rate in the column photobioreactor was obtained with an airflow rate of 8L/min. The results of the present research show that microalgae cultivation in wastewater has a great potential to reduce contamination while generating economic benefits, as microalgae biomass is widely used as a feedstock, and high-value products can be obtained from it.